Two manufacturing methods related to different aspects of forming metal tubing have typically been practiced independently, cutting to length, and forming to shape. Cutting metal tubing to length is generally done by some mechanical method and apparatus. Most commonly, tubing is simply cut, as by sawing, or scored and fractured by bending transverse to the axis of the tube. Scoring and fracturing is done when it is desired to minimize the chips and burrs that result from sawing, though doing so has the potential for bending and deforming the cut edge that is produced. This is because it is essentially impossible to provide a mandrel to support the interior of the tube around the fracture line. One proposal for a fractured cutting method that provides a cleaner edge is disclosed in U.S. Pat. No. 3,567,088 issued Mar. 2, 1971 to George L. Anderson. In one embodiment, a solid, but split, mandrel is inserted in the interior of the round tubes, with the two ends of the split mandrel abutted in a plane. Then a shear force is applied, perpendicular to the tube axis, along the plane between the abutted mandrel ends. This works well when the cut edge is simple, and also lies in a plane, but not otherwise. In another embodiment, the interior of the tube is pressurized with a fluid that is injected between two interior plugs that border the shear plane. The tube is then sheared along the plane in the same fashion. Not only does this work only when the cut edge lies in a plane, but the shearing action allows pressurized fluid to escape. Another proposal for avoiding the deformed edge produced by scoring and bending is disclosed in U.S. Pat. No. 5,133,492 issued Jul. 28, 1992 to Wohrstein, et al. A score line or groove is cut into the tube wall as usual, but the two parts of the tube are pulled straight apart, along the tube axis, rather than snapped apart perpendicular to the axis. As a practical matter, there is still deformation of the edge produced, just in a different direction.
Forming tubes to shape is increasingly done by hydroforming. A tube blank, usually a simple cylindrical tube, is clamped between a pair of die cavities that create a surrounding hollow space that is typically larger in circumference than the tube blank, although some areas may be smaller. The ends of the tube are sealed and its interior is highly pressurized to forcibly expand it out into the shape of the surrounding space. Complex shapes can be produced in this fashion, such as the beam members of a vehicle body frame or engine cradle. Welding and cutting operations are eliminated, at least as to each of the separate beam members, which themselves would otherwise have to be fabricated and welded from separate pieces. However, the beam members must still be welded or otherwise secured together at their ends. This requires cutting the formed tube to length, and, often, the cut ends must have a complex shape in order to be adequately welded to the other formed tubes that make up the frame. The cut off methods described above are inadequate for that task. Whatever cutting method is used, it is a separate, independent task that follows the hydroforming process itself, adding time and expense.